PROJECT SUMMARY To sustain the health of tissues in the body, the circulatory system needs to efficiently and continuously supply O2 and nutrients to every cell within the tissue. Capillaries, the site of gas exchange between circulating red blood cells (RBCs) and the surrounding tissue, constitute a majority of the vasculature. Yet, how?and in fact whether?the traverse of RBCs through the thousands of miles of branching capillaries to cells in need is a regulated remains unknown. This 5-year proposal focuses on pericytes located at capillary junctions and their role in regulating capillary blood flow. Pericytes, a type of contractile perivascular cell, have multiple projections that wrap around capillaries, and in so doing, can regulate the passage of RBCs. Preliminary data presented in this proposal show that pericytes, unlike other muscle cells, are capable of compartmentalized contraction and constriction of different branches of a junction. We hypothesize that pericytes play an important and novel role in structurally and dynamically changing the shape of junctions to insure the proper distribution of RBCs. In addition, the proposal will examine the molecular players involved in pericyte contraction, in particular, the mechanism that allows for a mode of contraction different from that of other muscle cells. The loss of pericytes is a hallmark of many cardiovascular and neurodegenerative illnesses, yet little is known about how the absence of pericytes affects blood flow and the pathogenesis of diseases. The current proposal will contribute to the career development of Dr. Albert L. Gonzales as he transitions from a postdoctoral associate to an independent researcher. Adding to his strong background in smooth muscle physiology, the candidate will develop new skills in state-of-the-art techniques, including in vivo multiphoton microscopy with next-generation genetically encoded Ca2+ indicators and optogenetic actuators. The University of Vermont is internationally recognized for its trainee development and productive research environment in vascular physiology. Mark Nelson, Ph.D. will serve as mentor for the candidate's scientific development. Dr. Nelson is a recognized leader in the field of vascular biology and has had 25 trainees who are now extramurally funded tenure-track faculty members at internationally and nationally ranked universities. To enhance the Candidate's training, the program additionally enlists internationally recognized experts, including Drs. Maiken Nedergaard, George Wellman, and Nikolaos Tsoukias. In this productive research environment, the candidate will establish a scientific niche and strengthen his transition to an independent research career.